package com.zhou.servlet;

import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;

public class ImageServlet extends HttpServlet {
    private String makeNum(){
        Random random = new Random();
        StringBuffer sb = new StringBuffer();
        for (int i = 0; i < 7; i++) {
            sb.append(random.nextInt(9) + "");
        }
        return sb.toString();
    }

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //如何让浏览器5秒刷新一次
        resp.setHeader("refresh", "3");
        //在内存中创建图片
        BufferedImage bufferedImage = new BufferedImage(80, 20, BufferedImage.TYPE_INT_RGB);
        //得到图片
        Graphics2D g = (Graphics2D) bufferedImage.getGraphics();
        g.setColor(Color.WHITE);
        g.fillRect(0, 0, 80, 20);
        g.setColor(Color.BLUE);
        g.setFont(new Font(null, Font.BOLD, 20));
        g.drawString(makeNum(),0, 20);
        resp.setContentType("image/jpeg");
        //网站存在缓存，不让浏览器缓存
        resp.setDateHeader("expires",-1);
        resp.setHeader("Cache-Control","no-cache");
        resp.setHeader("Pragma","no-cache");

        //把图片写给浏览器
        ImageIO.write(bufferedImage,"jpg", resp.getOutputStream());

        
        
        
        
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        super.doGet(req, resp);
    }
}
